If users see all images (product in use, from different angles, closer and further, in detail) they will be more motivated than users who just see the main image which eventually will help you to sell products.

That's why it's very important to show image thumbnails instead of just little grey dots as many ecommerce stores do. It really motivates users to browse product photos.

If we turn to Baymard' user research about image thumbnails on product pages, we will find that only 24% of e-commerce stores use it.

Here's the their conclusion about usage of thumbnails:

As you already understood, thumbnails should be visible not only on the desktop version (where they are already presented on most sites, check yours) but also in the mobile version (76% of stores still don't do it)

Here's a bad example from Fashionnova
They have dots, but it's not the option as it causes some users to miss the product images they were looking for, while others can have difficulty interacting with the indicator dots.

Here's an even worse example from Mavi:
They don't have even dots so users do not understand what other product pictures exist, how many there are. As a result, it negatively affects the shopping process.

Here are good examples from American Eagle and VictoriaSecret
They show thumbnails for all available product images as it's tremendously important in users' product-evaluation experience, providing critical visual information about key product details.